1. Field of the Invention
The present invention relates to a rotary compressor, and more particularly to a resonator for a rotary compressor which prevents generation of impact exciting force and pulsation sound occurred due to pressure pulsation and reduces a noise of a low frequency band generated in the compressor by forming a curved portion at a narrow unit of the resonator which is a pressure pulsation inflow path and controlling the ratio of dimensions of the narrow unit and a resonance unit, for thereby smoothing the inflow of the pressure pulsation generated from a pressure chamber.
2. Description of the Conventional Art
Generally, a compressor which constitutes a cooling cycle device such as an evaporator, an accumulator, etc. is an apparatus that compresses air or coolant gas by the rotation of an impeller or a rotor, or the reciprocation of a piston, the compressor consisting of a power unit system for driving the impeller, the rotor or the piston and a compression unit for sucking and compressing gas by the driving force transmitted from the power unit system.
Such a compressor is divided into two types, a hermetic type and a separate type, in accordance with a layout of the power unit system and the compression unit. According to the hermetic type, the power unit system and the compression unit are disposed together in a predetermined hermetic vessel, while as for the separate type the power unit system is located out of the hermetic vessel so that the driving force generated from the power unit system is transmitted to the compression unit in the hermetic vessel, the hermetic compressor being divided into, according to a system of compressing the gas, rotary, reciprocating, linear and scroll compressors.
In the conventional rotary compressor among the hermetic type compressors, as shown in FIG. 1, a compression unit and a motor unit for driving the compression unit are installed in a hermetic vessel 1 of a hollow cylindrical shape wherein a crank axle 4 is provided, the compression unit and the motor unit performing compressing of a coolant gas which is flowed into the hermetic vessel 1, in accordance with the power application.
More specifically, in the motor unit, a stator 2 is fixed to an inner wall of the hermetic vessel 1, a ring-shaped rotor 3 is installed in the stator 2 and the crank axle 4 is pressedly inserted in the rotor 3, so that when magnetic force is generated in the stator 2 in accordance with the power application, the rotor 3 rotates by virtue of induced electromotive force which is produced by the interaction between the rotor 3 and the stator 2 and accordingly the crank axle 4 rotates in conjunction with the rotor 3.
Further, the compression unit, as shown in FIG. 2, is provided with a roller 5 which is eccentrically disposed at a bottom of the crank axle 4 and performs suction, compression and exhaust of the coolant while rotating having a certain eccentric track in accordance with the rotation of the crank axle 4, a cylinder 6 which has a slot 9 at an inner wall thereof, the slot 9 having a vane 12 which separates a suction chamber 10 and a compression chamber 11 while reciprocating therein in accordance with the rotation of the roller 5, a main bearing 7 and a sub bearing 8 that support the compression unit at upper and lower parts of the cylinder 6, a suction inlet 13 and an exhaust outlet 14 which are flow paths of the coolant that is sucked/exhausted to/from the cylinder 6, and a muffler 15 disposed at an upper portion of the exhaust outlet 14 in order to reduce the exhaust noise, so that the compression unit compresses and exhausts the coolant which has been flowed through the suction inlet 13 into the cylinder 6.
In the thusly configured rotary compressor, when the magnetic force is generated from the stator 2 by the power application, the rotor 3 rotates by the induced electromotive force, thereby rotating the crank axle 4 which is pressedly inserted therein. Then, the roller 5 which is eccentrically disposed at the bottom of the crank axle 4 revolves itself and around an inner circumferential surface of the cylinder 6 while having the certain eccentric track, thereby generating suction force, so that the coolant gas is flowed through the suction inlet 13 to the suction chamber 10.
Next, when the roller 5 further rotates for predetermined degrees, the compression of the coolant starts. Here, when the rotation degrees become around 200.degree., the pressure in the compression chamber 11 becomes identical with or greater than the exhaust pressure, so that an exhaust valve (not shown) of the exhaust outlet 14 is open, thereby exhausting the compressed coolant gas. Then, the coolant gas which has been exhausted through the exhaust outlet 14 passes through the muffler 15 disposed at the upper part of the main bearing, rapidly expands into an inner space of the compressor and is flowed outside of the compressor through an exhaust pipe (not shown).
However, during which the above operation is repeated, pressure pulsation is generated in the process of compressing and exhausting the coolant and the impact vibration due to the pressure pulsation is travelled to the cylinder 6 which constitutes the compression unit, thereby vibrating the cylinder 6 and the hermetic vessel 1 and thus radiating the noise to the outside of the compressor. Also, strongly directional resonant sound is radiated outside of the compressor by which in the exhaust of the coolant pressure pulsation elements which are generated in the cylinder 6 rapidly expand into the inner space of the compressor, thereby exciting a sound mode thereof.
Accordingly, in the conventional rotary compressor a resonator is disposed in a middle part of the exhaust path in order to relieve the pressure pulsation which is generated in the coolant compressing process and prevent the rapid flow of the pressure pulsation during the exhausting performance.
FIG. 3 illustrates a resonator 16 of the conventional rotary compressor, which consists of a narrow unit 16a serves as an inflow path of the pressure pulsation and a resonance unit 16b attenuates the pressure pulsation flowed through the narrow unit 16a. Further, a frequency band for the resonator 16 is determined in accordance with size of a resonant space unit, and area and length of a pressure inflow path.
Meanwhile, 4 KHz is generally known as a frequency to which people have the most keen sense of hearing, and accordingly as for the resonator for the conventional rotary compressor the specification of each element has been determined to correspond with an objective frequency, considering only a frequency band adjacent 4 KHz.
However, in such a conventional resonator, since an edge is formed in a pressure pulsation inlet port of the narrow unit 16a which communicates with the exhaust outlet, the pressure pulsation elements flowed into the resonator side collide with this portion, thereby generating the vortex, so that the exhaust of the compressed coolant is obstructed and the attenuation of the pressure pulsation of the resonator is weakened, which results in increase in the flow noise.
In addition, in accordance with the recent trend of being a large-sized compressor, the compression space of the cylinder increases and accordingly the size of the compression unit and the hermetic vessel which finally radiates the noise is also increased, so that the main frequency elements of the noise which is radiated from the compressor are moved to a low frequency band. Therefore, the limits are found in the conventional resonator for the rotary compressor designed only for the 4 KHz frequency band and thus another type of the resonator suitable for the increased capacity of the compressor has been required.
Particularly, when the compressor is installed in an air conditioner, the noise can be intercepted at some extent if appropriately using a sound absorption member with respect to the high frequency noise elements adjacent to 4 KHz, but to the noise elements of the low frequency band the absorption effect is reduced, thereby causing louder grating noise.